Subject: [syzbot] [bpf?] WARNING: bad unlock balance in bpf

From: syzbot <[email-masked]>
Date: Fri, 26 May 2023 03:10:56 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    c4c84f6fb2c4 bpf: drop unnecessary bpf_capable() check in ..
git tree:       bpf-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=119576a9280000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8bc832f563d8bf38
dashboard link: https://syzkaller.appspot.com/bug?extid=8982e75c2878b9ffeac5
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10391dde280000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=137da9c5280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3cb57feeb883/disk-c4c84f6f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7ccb6d78c42d/vmlinux-c4c84f6f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fb02c9cdb21c/bzImage-c4c84f6f.xz

The issue was bisected to:

commit c4c84f6fb2c4dc4c0f5fd927b3c3d3fd28b7030e
Author: Andrii Nakryiko <[email-masked]>
Date:   Wed May 24 22:54:19 2023 +0000

    bpf: drop unnecessary bpf_capable() check in BPF_MAP_FREEZE command

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17b7214d280000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1477214d280000
console output: https://syzkaller.appspot.com/x/log.txt?x=1077214d280000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]
Fixes: c4c84f6fb2c4 ("bpf: drop unnecessary bpf_capable() check in BPF_MAP_FREEZE command")

=====================================
WARNING: bad unlock balance detected!
6.4.0-rc1-syzkaller-00358-gc4c84f6fb2c4 #0 Not tainted
-------------------------------------
syz-executor518/5004 is trying to release lock (&map->freeze_mutex) at:
[<ffffffff8193e2c4>] map_freeze kernel/bpf/syscall.c:1951 [inline]
[<ffffffff8193e2c4>] __sys_bpf+0x3234/0x5520 kernel/bpf/syscall.c:5078
but there are no more locks to release!

other info that might help us debug this:
no locks held by syz-executor518/5004.

stack backtrace:
CPU: 0 PID: 5004 Comm: syz-executor518 Not tainted 6.4.0-rc1-syzkaller-00358-gc4c84f6fb2c4 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/16/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
 __lock_release kernel/locking/lockdep.c:5368 [inline]
 lock_release+0x4f1/0x670 kernel/locking/lockdep.c:5711
 __mutex_unlock_slowpath+0x99/0x5e0 kernel/locking/mutex.c:907
 map_freeze kernel/bpf/syscall.c:1951 [inline]
 __sys_bpf+0x3234/0x5520 kernel/bpf/syscall.c:5078
 __do_sys_bpf kernel/bpf/syscall.c:5185 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5183 [inline]
 __x64_sys_bpf+0x79/0xc0 kernel/bpf/syscall.c:5183
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f7eb20e8bb9
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffe49d4848 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f7eb20e8bb9
RDX: 0000000000000004 RSI: 0000000020000180 RDI: 0000000000000016
RBP: 00007f7eb20acd60 R08: 0000000000000000

---
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